Appliances such as air conditioners and the like are typically fitted with drain pans for catching accumulated fluid resulting from operation of the appliance. Such drain pans are generally provided with a drain fitting for draining the accumulated fluid away from the appliance. These drain fittings are sometimes rendered inoperative by the occlusion of the outlet due to the presence of foreign matter, such as insects, algae, etc. Some prior art devices have provided an additional drain outlet opening to remove the accumulated fluid when the primary drain outlet becomes occluded. These additional drain outlet openings essentially comprise a duplicate of the primary drain outlet, although positioned at a higher location so that they only function when the fluid level in the pan rises due to occlusion of the primary drain. Moreover, as water drains from the air conditioner pan it passes through a trap in the drain line. The water in this trap prevents air from being drawn up through the drain pipe by the air conditioner recirculation fan. When the air conditioner is not operated for a long period of time, i.e. the winter season, the water in the trap evaporates. This allows a current of air to enter the air conditioner pan through the drain opening, preventing condensate from draining properly through the drain opening. This, in turn, causes an overflow of water until the air conditioner unit cycles off and water is allowed to enter the drain and fill the trap.
Other prior art devices, such as found on room dehumidifiers, for example, have reservoirs for catching water removed from the ambient air during operation of the appliance. These devices may have a float operated switch for shutting off the appliance when the reservoir becomes full.
Examples of prior art devices are disclosed in the following U.S. Pat. Nos.: 977,055, 1,188,603, 1,907,299, 3,205,676, 3,236,061 and 3,910,061. None of these patents, whether considered singly or in combination, teach an emergency drain for air conditioners in which collected fluid is evacuated from the air conditioner drain pan when the primary drain becomes occluded, nor do they teach a one-way valve in the drain line for preventing flow of air or other fluid back through the drain and into the drain pan.